transpile: Cast overflow builtin operands to the output type#1863
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thedataking wants to merge 1 commit into
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transpile: Cast overflow builtin operands to the output type#1863thedataking wants to merge 1 commit into
thedataking wants to merge 1 commit into
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The overflow builtins lower to `overflowing_*`, which requires both operands to share the receiver's type. Surfaced by transpiling libgit2.
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@thedataking I don't think there is any overlap between the two PRs, since this one deals with the parameter types and not the actual result type of the function. |
ahomescu
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Jun 19, 2026
| let [a, b, c]: [_; 3] = args | ||
| .try_into() | ||
| .map_err(|_| "`convert_overflow_arith` must have exactly 3 arguments")?; | ||
| let a = mk().cast_expr(a, result_ty.clone()); |
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gcc is being very loose with the type system here:
These built-in functions promote the first two operands into infinite precision signed type and perform addition on those promoted operands. The result is then cast to the type the third pointer argument points to and stored there. [...] The first built-in function allows arbitrary integral types for operands and the result type must be pointer to some integral type other than enumerated or boolean type
I'm not sure casting to the result type is correct here.
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Possibly superseded by the broader builtin type-handling rework in #1860 / #1707. Tagging @Rua for coordination.